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GLOBAL SEASONAL CLIMATE UPDATE
TARGET SEASON: May-June-July 2021
Issued: 24 April 2021
WEATHER CLIMATE WATER
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Summary
Observed sea surface temperatures (SSTs) in the central tropical Pacific were in a weak La Niña condition during January-February-March 2021. The below-normal sea-surface temperature anomalies in the Niño 3.4 and Niño 3 regions, both of which are used to characterize ENSO conditions, are predicted to return towards normal condition during the May-June-July 2021 season. SST anomalies in other tropical ocean basins are generally predicted to be in near normal conditions.
For May-June-July 2021, no land area is predicted to have below-normal air temperature. Above-normal air temperatures over land are expected to be strongest over the southern half of North America, and over northern Asia. Above-normal temperatures are also expected in the northern regions of central America, Caribbean, western Asia (including Arabian Peninsula), northern Africa, Europe, eastern and central Asia. Above-normal temperatures are also likely over much of the northern high latitudes. In the Northern Hemisphere, other areas where above- normal temperatures are most likely include much of south Asia and the maritime continent, while there is no clear signal over the Indian subcontinent. In the Southern Hemisphere, there is more uncertainty about the expected air temperatures, although there is a higher chance that the southern and north-eastern parts of South America will be above-normal. Over Australia, in general, there is no clear signal while New Zealand is expected to have above- normal temperature.
Some of the predicted rainfall anomalies for May-June-July 2021 represent a lingering influence of decaying La Niña conditions. These impacts include increased chances of dry conditions in the equatorial Pacific near the dateline extending south-eastward into the southern part of South America. Probabilities for below-normal rainfall also extend through western Asia, southern half of North America, southern regions of central America, and the Caribbean. There are increased probabilities of above-normal rainfall over the Indian subcontinent, and over the far northern part of South America.
Surface Air Temperature, MJJ 2021 Precipitation, MJJ 2021
Figure 1. Probabilistic forecasts of surface air temperature and precipitation for the season May-June-July 2021. The tercile category with the highest forecast probability is indicated by shaded areas. The most likely category for below-normal, above-normal and near-normal is depicted
in blue, red and grey shadings respectively for temperature, and orange, green and grey shadings respectively for precipitation. White areas indicate equal chances for all categories in both cases. The baseline period is 1993–2009.
3 Figure 2. Observed January-February-March 2021 near-surface temperature anomalies relative to 1981–2010. (Source: U.S. Climate Prediction
Center).
4 Figure 3. Observed January-February-March 2021 precipitation anomalies relative to 1981–2010 base period (top). (Source: U.S. Climate
Prediction Center).
